I read this book to my 6-year-old over the course of many weeks. She really enjoyed it (as did I). A good children's fantasy with an adventurous heroine, a foreign planet, exotic creatures, and a mystery. Nothing amazing or earth-shattering, but an engaging story (and I totally cried at the end). The book also includes a large illustration at the beginning of each chapter (and sometimes one within the chapter), which really helped her visualize some of the creatures and habitats being described.
We read 1-2 chapters a night, until the end when we blasted through like 6 chapters on a Sunday afternoon. Some of the language was beyond her, but we'd stop and talk about anything she didn't immediately understand. For an older kid, this would be a fun read on their own. For a Kindergarten or 1st grader with good reading skills and a long-ish attention span it's a great bedtime read!